<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .activate {
        color: red;
      }
    </style>
  </head>
  <body>
    <div id="root"></div>

    <script
      src="https://unpkg.com/react@18/umd/react.development.js"
      crossorigin
    ></script>
    <script
      src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"
      crossorigin
    ></script>
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>

    <script type="text/babel">
      const root = ReactDOM.createRoot(document.querySelector('#root'))

      class App extends React.Component {
        constructor() {
          super()

          this.state = {
            movies: ['星际穿越', '流浪地球', '大话西游'],
            currentIndex: 0
          }
        }

        btnClick(index) {
          this.setState({
            currentIndex: index
          })
        }

        render() {
          const { movies, currentIndex } = this.state

          const liEls = movies.map((item, index) => (
            <li
              className={currentIndex === index ? 'activate' : ''}
              key={item}
              onClick={() => this.btnClick(index)}
            >
              {item}
            </li>
          ))

          return <ul>{liEls}</ul>
        }
      }

      root.render(<App />)
    </script>
  </body>
</html>
